Ds1 was like this for over a year.
I would give him a spray of rescue remedy to help his body relax.

A friend used a herbal sleep remedy a homeopath made for her and that worked well. Think it had Bach flowers that were good for her child.

Otherwise just cuddle them. Same as tantrums, holding them helps them to "know" they are safe

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unless someone like you cares a whole awful lot, nothing is going to get better. its not.
Dr Seuss